The subject matter disclosed herein relates to medium to high voltage power systems, such as switched mode power supplies. Specifically, the subject matter relates to planar transformers utilized in switched mode power supplies. In recent years, planar transformers have gained acceptance in various switched mode power supply technologies, as they offer numerous technical and commercial advantages over more traditional power transformers.
Generally, planar transformers are manufactured using printed circuit boards (PCBs). A magnetic core is attached to a multilayer PCB. High and low voltage coils are created by depositing thin, wide copper traces in spiral patterns around the magnetic core on the various layers of the PCB. During operation, one of the coils is selected as the primary winding, and the other coil is designated as the secondary winding. A varying current is applied to the primary winding, which induces a varying magnetic field in the magnetic core. This in turn leads to a varying voltage induced within the secondary winding.
Because planar transformers are manufactured using PCBs, manufacturers are able to take advantage of the well-known design and manufacturing methods for PCBs. For example, planar transformers have a predictable design method based on known and controlled material properties and geometrical tolerances in conventional PCB technology. Planar transformers may also have a shorter manufacturing time, lower fabrication cost, and lower assembly cost than traditional transformers. However, previous designs for planar transformers have not always been capable of reliable operation in medium to high voltage power converters. For example, previous attempts at high voltage isolation within planar transformers do not have sufficient margin to avoid undesired partial discharge. Accordingly, it would be desirable to manufacture a planar transformer using PCB technology for use in medium to high voltage power converters.